docs: def set_source_nodes(self, source_nodes):
          r"""
          Set the source nodes and compute their t-weights.
          
          Parameters
          ----------
          source_nodes : sequence of integers
              Declare the source nodes via their ids.
          
          Notes
          -----
          It does not get checked if one of the supplied source-nodes already has
          a weight assigned (e.g. by passing it to `set_sink_nodes`). This can
          occur when the foreground- and background-markers cover the same region. In this
          case the order of setting the terminal nodes can affect the graph and therefore
          the graph-cut result.
          """
          self.__snodes = list(source_nodes)
          
          # set the source-to-node weights (t-weights)
          for snode in self.__snodes:
              self.__tweights[snode] = (self.MAX, 0)